Electric and hybrid electric vehicles often use sources of high voltage such as battery packs or fuel cells that deliver direct current (DC) to drive vehicle motors, electric traction systems, and other vehicle systems. These systems typically include power inverters to convert the DC input from the power source to a 3-phase alternating current (AC) output compatible with electric motors and other electrical components. Such inverters generally include both power and capacitor modules interconnected by a bipolar busbar system that distributes current throughout the inverter. Such busbar systems often involve two or more intricately designed busbars or busbar electrodes that overlap for most of the area of the busbar system.
Moreover, some conventional inverters have been observed to incur voltage spikes when currents flowing through the power module abruptly change, such as when the inverter is switched on or off. The magnitudes of these voltage spikes are related, at least in part, to the inductance of the busbar. More particularly, the relationship between inductance (L), current (i), voltage (V), and time (t) is described in equation (1):V=L*(di/dt)  (1)This equation demonstrates that voltage spikes are intensified for systems that have a high inherent inductance. That is, even relatively small changes in current can produce relatively large voltage spikes if the inductance is high. A busbar system may contribute substantially to the total inductance of an inverter system because of the relatively long current pathway between its various input and output terminals.
Many busbar design factors such as the amount of overlap between positive and negative electrodes can affect the inductance of a busbar system. Because current flows in opposing directions in each electrode, this overlap effectively reduces the overall inductance of the busbar. As a result, many busbar system designs include positive and negative electrodes configured as a laminar structure electrically separated by a non-conducting layer. While these designs offer an overlapped current pathway for the majority of area on a busbar system, the interconnecting elements that transfer current from a primary busbar to a connected subsystem, such as a power module, have non-overlapping components. Accordingly, the contribution of such elements to overall system inductance can be significant. Further, connector terminals on each electrode are typically separated from each other and thus require separate fasteners. While such separation helps to prevent shorting between electrodes, part count and assembly complexity are both increased as a result.
Accordingly, it is desirable to provide a low inductance busbar assembly that reduces voltage spikes when power modules are switched on or off. Further, it is also desirable if such a busbar assembly has a reduced part count and material cost, and is simpler to assemble. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.